This invention relates to the securing of doors, specifically to the securing of a door with an apparatus that utilizes the securing strength available through connection to the floor, but without leaving parts of the securing apparatus in the pathway of the door.
Forced entry through doors supposedly designed to provide privacy and security to occupants behind the doors is a problem that has long been worrisome to occupants. Simple knobs can only serve to prevent a person from entering who is not willing to turn the knob and enter. A locking device that prevents the knob from turning when locked is an answer to that problem. Forcefully entering any locked door is, however, only limited by the amount of force a person trying to enter is willing to apply to the door. The purpose of an apparatus designed to secure a door is to make the force required to enter a locked door greater than is practically available to a perpetrator. A method of forcing open a door would not be practically available if it was either physically beyond the capability of a perpetrator or demanded adequate time and energy for the perpetrator to be discovered by the authorities.
As a failure mechanism, a door assembly may yield through three main modes. First, the door itself may rupture. Most doors are significant enough that if adequate force is applied to the door to rupture the door, there will be a great deal of noise associated. U.S. Pat. No. 5,154,461 provides a bar along the middle section of a door that it claims would strengthen that portion of the door. That invention claims that such a strengthening would be especially significant in adding support to "hollow-core" doors. That claim does seem reasonable, but hollow-core doors are typically not used where security is a main function of the door. Even where such a door might be used for security, destruction of the hollow-core door by brute force would create a significant disturbance and would be likely to require greater force than other means of entry.
The second failure mode would be for the door latch bolt or hinges to fail. Shearing of the bolt or hinges is very unlikely because of the relative strengths of the metal of which the bolt or hinge is made compared to the wood to which the bolt or hinge is typically connected. If the door jam were constructed of metal, a determination of where the failure would occur would be a closer question. With all metal construction, however, the force required to force open the door would be quite significant and would be likely to be beyond the capability of most perpetrators. Those that could force entry would be more noticeable in their efforts. Very little in the prior art is directed to the strengthening of the door latch bolt or the hinge pins. This is logical since the bolt and hinges connect directly to the weakest link in the door locking mechanism.
The weakest link in the door locking mechanism is the door jamb at the latch bolt. This, along with tear-out of the connection devices that hold the hinges in place, is the third mode of failure. Failure at the latch bolt is more likely than failure at the hinges because the hinges are far apart, typically have more connectors, and would be hard to strike simultaneously. It is evident why a door jamb in a residence is likely to be the typical failure element when the jamb's characteristics are considered. The typical residential door jamb is constructed of wood. The wood is oriented such that a force applied to the door latch bolt will be transferred to the wood perpendicular to the grain of the wood and relatively near to the edge of the wood. Wood has very poor tensile strength perpendicular to the grain. Therefore, when relatively little force is applied to the jamb through the latch bolt, the jamb is split and the door swings open. U.S. Pat. Nos. 5,154,461 and 5,199,759 both recognize this problem specifically. The '461 patent attempts to strengthen the connection at the jamb by putting more and longer screws into the jamb through the striker plate to which the latch bolt connects. This must help some, but only provides limited additional strength since the wood in the jamb or a stud behind the jamb is still being loaded in tension perpendicular to the grain.
The '759 patent approaches the problem in a different way. Because of the limitations of the jamb, this patent looks for strength from the floor to provide security. The floor is essentially an enormous plate held in place by the weight of the building. If a secure connection can be made to the floor, a door can be held firmly in place. The '759 patent as well as U.S. Pat. Nos. 4,348,879, 4,673,203, 4,676,536, and 5,163,308 all rely on this principle to secure doors. Each of these, however, is limited in ways the present invention is not.
The '203 and '536 patents rely on jamming a member at an acute angle between the door and the floor. Such a member is, however, subject to slippage along the floor. The '879 and '308 patents require recesses to be created in the floor. This creates a problem because the recesses tend to fill up with dirt. The recesses tend to fill up because they are below a pathway. Such devices become inoperable unless they are cleaned out regularly. The '759 patent is not limited by either of these problems, but does create a practical problem. The anchor piece listed in each of its embodiments must be in the pathway of the door. Consequently, it must also be in the pathway of the persons using the door. The anchor piece is a tripping hazard. Further, in the second embodiment, the door sill anchors the wedge that holds the door. The sill is visible from the other side of the door and is subject to being manipulated from the outside.
Of all of the prior patents listed above, only the '461 patent allows for operation from outside of the building. This means that unless the occupants are inside the building, or leave the building from some other exit, the security of the supplementary device cannot be utilized. If the occupants were to leave by some other exit that did not have a supplementary security device, it is likely that the other exit could be manipulated for entry and thus the security of the supplementary device would be defeated. Though the '461 patent does provide operation from outside of the building, it does not connect to the floor and is therefore limited in strength by the strength of the door jamb. The present invention can be configured to operate from outside of the building through a locking device and linkages which can engage and disengage the cross bar.
It is therefore an object of the present invention to provide an apparatus for securing a door which is connected directly to the floor.
It is further an object of the present invention to provide an apparatus for securing a door which is located above floor level and requires little or no maintenance.
It is further an object of the present invention to provide an apparatus for securing a door which is outside of the pathway unless the door is in the secured position.
It is further an object of the present invention to provide an apparatus for securing a door which is beyond the reach of manipulation from the other side of the door.
It is further an object of the present invention to provide an apparatus for securing a door which can be operated from either side of the door and thus allows for use of the securing device when a building is not occupied.